JP2002033703A - Optical reception fault diagnostic method, and optical transmission system provided with optical reception fault diagnostic function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method that can easily discriminate whether a fault location exists in a station or in a device and further in a transmitter or in a receiver through remote location, on the occurrence of an optical interruption fault and to provide an optical transmission system. SOLUTION: A center 3 can easily discriminate whether a fault location exists in a transmission line 50 or in optical transmission systems and further in an optical transmitter 10 or in an optical receiver 20, through its remote control on the occurrence of an optical interruption fault by providing an optical switch 30 to an input section of an optical signal and an optical branch 40 to an optical output section in both bidirectional optical transmission systems 1, 2 so as to provide a loopback function of input and output lights.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing an optical reception failure in an optical transmission apparatus and an optical transmission system having this function.

[0002]

2. Description of the Related Art High-speed, large-capacity optical communication systems have been developed with an increase in communication traffic. The larger the system, the larger the capacity, the more severe the damage in the event of a failure,
It is necessary to be able to judge the content of the failure as soon as possible. 2
FIG. 4 shows a basic configuration of a bidirectional optical communication system between stations. The A station 60 includes an optical transmitter A52 and an optical receiver A53, and the B station 70 also includes an optical receiver A54 and an optical transmitter A5.
The optical transmission line 56 and the optical transmission line 51 connect the optical transmitter and the optical receiver between the stations.
Now, if a received light level failure (LOS) is detected in the optical receiver B54 of the B station 70, the cause is a failure of the optical transmitter A52 of the A station 60, a failure of the optical receiver B54 of the B station 70, or The degradation or disconnection of the optical transmission line 51 can be considered, and even if a received optical level failure is detected by the optical receiver A53 of the A station 60, the corresponding optical transmitter, optical receiver and optical transmission The road may be faulty. In order to speed up recovery, it is necessary to isolate these failures and identify the cause of the failure.

[0003] In an optical communication system in which transmission lines and terminal devices are not duplicated, a conventional technique for detecting such a failure is disclosed in Japanese Patent Application Laid-Open No. 5-63645. The invention shown in FIG. 6 shows a configuration as shown in FIG. That is, the A station 6 determines whether the failure has occurred in the optical transmitter B55 of the B station 70 or the failure in the optical transmission line 51.
In order to judge from the 0 side, the 2 × 1 optical switch 57, the optical receiver B54 and the optical transmitter B55 are monitored on the B station 70 side, and the transmission light from the A station side is looped back. Is provided with an optical switch control unit 58 for controlling the optical switch 57, a signal looped back to the A station 60 side is received by the optical receiver A53, and a failure of the optical transmitter B55 on the B station side or an optical transmission path is detected. Failure determination unit 59 for detecting whether the failure is 51
Is provided. With this configuration, it is only necessary to monitor only the optical transmission line and the B station side for a failure in the optical transmitter.
It is not possible to cope with the determination of various possible causes of failure as described above. In addition, since the optical receiver A53 can receive the light looped back and forth in the optical transmission line 51 at the minimum light receiving level because of the simple optical loopback configuration, it is necessary to allow the optical receiver A53 between the A station and the B station. The transmission line loss becomes half of the normal loss, and in the case of a relay device or the like, the relay interval becomes short, which is not practical.

[0004] In an optical transmission device, the transmission light level of an optical transmitter is monitored (BACK PIN monitor) by a PIN photodiode housed in the same package for light emitted from behind a laser diode as a light source. There is also. If a transmitter having such a BACK PIN monitor function has a light receiving level failure in a receiver provided in an opposite receiving device and the BACK PIN monitor alarm on the transmitting side does not appear, the cause of the failure is transmitted. It may be judged that it is on the road. However, BACK
The PIN monitor alarm cannot be tested at the time of shipment from the factory, and cannot be said to have high reliability. For this reason, when a site is actually investigated when a failure occurs, there is a case where there is no abnormality in the transmission path and the laser diode of the transmitter is destroyed. On the other hand, the receiver cannot detect a physical failure of the PD or APD of the light receiving element and cannot distinguish it from a transmission line failure. Will be needed.
Such troublesome trouble determination may lead to a large increase in maintenance cost depending on the condition of the field such as undersea relay.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art. It is an object of the present invention to provide an optical communication system in which the cause of a failure in an optical interruption is within a station or an office. It is an object of the present invention to provide an optical reception failure diagnosis method capable of easily determining whether or not a device is in an apparatus, and further distinguishing a transmitter and a receiver by a remote operation, and an optical transmission system having this function.

[0006]

To achieve the above object, an optical transmission system according to the first aspect of the present invention comprises an optical transmitter, an optical receiver, and a part of an optical output from the optical transmitter. A plurality of bidirectional optical transmission devices connected to the transmission and reception side optical transmission line, comprising:
The apparatus further includes a failure monitoring control unit that monitors reception failures of the plurality of optical receivers included in the plurality of bidirectional optical transmission devices and controls the optical return unit. Also,
The optical transmission system according to the second aspect of the present invention is the optical transmission system according to the first aspect,
An optical branching unit that outputs an optical output from the optical transmitter to the optical transmission line on the transmitting side to a main output light and a branched light obtained by branching a part of the optical output; and an optical transmission line output on the receiving side. And a switch for switching between light and the branch output light of the branching means and connecting to the optical input of the optical receiver. Further, in the optical transmission system according to the third aspect of the present invention, the control performed by the fault monitoring control means according to the first aspect of the present invention is the optical transmission system according to the second aspect of the present invention. The switching connection is controlled. Also, an optical transmission system according to the invention according to claim 4 of the present invention is the optical transmission system according to claims 1 and 2, wherein the optical turn-back means outputs an optical output output from the optical transmitter to an optical transmission path on a transmission side. The branching ratio of the means for partially branching is smaller than -10 dB. An optical transmission system according to a fifth aspect of the present invention is the optical transmission system according to the first and second aspects, wherein the optical turn-back means connects the branch output light to an optical input of the optical receiver. Is substantially equal to the input light level of the optical receiver during the bidirectional transmission. Further, the optical reception failure diagnosis method of the invention according to claim 6 of the present invention comprises:
An optical transmitter, an optical receiver, and an optical branching unit that outputs an optical output that is output from the optical transmitter to an optical transmission line on a transmission side to a main output light and a branched light that partially branches the optical output. A light return means for switching the output light of the optical transmission path on the receiving side and the output light of the branching means and connecting to the optical input of the optical receiver, and connected to the optical transmission path on the transmitting and receiving sides. A plurality of bidirectional optical transmission devices, and a failure monitoring control unit that monitors reception failures of the plurality of optical receivers included in the plurality of bidirectional optical transmission devices and controls the switching connection of the optical return unit. In the optical transmission system provided,
The failure monitoring control means receiving information on occurrence of an optical reception failure from the optical receiver provided in one of the two-way optical transmission apparatuses performing bidirectional optical transmission with each other; and the failure monitoring control means Performing the control for changing the connection state of both the optical return means from the state at the time of the bidirectional optical transmission, and the fault monitoring control means, after controlling the connection state change of the optical return means, When receiving information that the optical reception failure is not cleared from the optical receiver included in the one bidirectional optical transmission device, the optical reception failure of the optical receiver itself included in the one bidirectional optical transmission device is the optical reception failure. When it is determined that the cause is an optical reception failure that has occurred during bidirectional optical transmission, and when the information on which the optical reception failure has been canceled is received, an optical reception failure of the optical receiver included in the other bidirectional optical transmission device is performed. Confirming that, when a new optical reception failure occurs in the optical receiver provided in the other bidirectional optical transmission device, the output failure of the optical transmitter provided in the other bidirectional optical transmission device is caused by the bidirectional It is determined that the cause of the optical reception failure occurred during optical transmission, and if no optical reception failure has newly occurred in the optical receiver provided in the other bidirectional optical transmission device, during the bidirectional optical transmission A step of determining that the optical transmission line to which the optical receiver in which the reception failure has occurred is connected is a cause of the optical reception failure that has occurred during the bidirectional optical transmission. An optical transmission system according to a seventh aspect of the present invention includes a plurality of optical transceivers each including an optical receiver and an optical transmitter having a different transmission wavelength, and an output of the plurality of optical transmitters having different transmission wavelengths. And a wavelength multiplexer for inputting the wavelength-multiplexed input light to the plurality of optical receivers for wavelength separation and connection, and having substantially the same transmission wavelength characteristics as the multiplexer. A demultiplexer, an optical branching unit for branching and outputting an optical output from the multiplexer to the transmission side optical transmission line into a main output light and a branch output light, and a reception side optical transmission line output light. An optical return unit for switching the branch output light of the branching unit and connecting to the optical input of the demultiplexer; and a plurality of the multiplexers connected to the transmission and reception side optical transmission paths. A bidirectional wavelength-division multiplexing optical transmission device having substantially the same transmission wavelength characteristic; Characterized in that it comprises a failure monitoring control means for controlling the switching connection of the monitor and the light folding means receiving failure of a plurality of the optical receiver included in the multiplex transmission equipment.
Also, the optical transmission system according to the invention according to claim 8 of the present invention branches and outputs the optical receiver having a different transmission wavelength from the optical receiver and the output light from the optical transmitter into the main output light and the branch output light. A first optical branching means, and a first optical turnaround means for switching between the output light of the optical transmission path on the receiving side and the branched output light of the first optical splitting means and connecting to the optical input of the optical receiver. A plurality of optical transceivers, a multiplexer for multiplexing main output lights of the first optical branching means having different transmission wavelengths, and outputting the multiplexed light to an optical transmission path on a transmission side, and a wavelength-multiplexed input. A wavelength divider for connecting the light to the plurality of optical receivers, and a demultiplexer having substantially the same transmission wavelength characteristic as the multiplexer, and an optical output from the multiplexer to the transmission-side optical transmission line. A second optical branching means for branching and outputting the main output light and the branch output light; an optical transmission line output light on the receiving side; A second optical return means for switching to a branch output light of an optical branching means and connecting to a light input of the demultiplexer; and a plurality of the multiplexing means connected to the transmission and reception side optical transmission lines. The transmission wavelength characteristics of the two-way wavelength division multiplexing optical transmission device having substantially the same transmission device, and monitoring the reception failure of the plurality of optical receivers provided in the plurality of bidirectional wavelength division multiplexing optical transmission devices and monitoring the first and second optical transmission devices. It is characterized by comprising fault monitoring control means for controlling the switching connection of the optical turn-back means. An optical reception failure diagnosing method according to the ninth aspect of the present invention includes a plurality of optical transceivers each including an optical receiver and an optical transmitter having a different transmission wavelength; and an optical transmitter having the plurality of different transmission wavelengths. A multiplexer for multiplexing the outputs of the optical receivers and outputting them to an optical transmission line on the transmission side, and wavelength-multiplexed input light is wavelength-separated and connected to the plurality of optical receivers. A demultiplexer that is substantially the same, an optical splitter that splits and outputs an optical output from the multiplexer to the transmission optical path on the transmission side into a main output light and a branch output light, and an optical transmission path output on the reception side. Light combining means for switching the light and the branch output light of the branching means to connect to the optical input of the demultiplexer, and a plurality of the multiplexing means connected to the transmission and reception side optical transmission lines. Two-way wavelength multiplexing optical transmission device having substantially the same transmission wavelength characteristics In the optical transmission system having a failure monitoring control means for controlling the switching connection of a plurality of monitored said light folding means receiving failure of the optical receiver included in the wavelength division multiplexing optical transmission equipment,
The failure monitoring control means, the step of receiving information on the occurrence of an optical reception failure from the optical receiver provided in one of the two-way wavelength multiplexing optical transmission device performing bidirectional wavelength multiplexing optical transmission, Fault monitoring control means for performing control for changing the connection state of both the optical return means from the state at the time of the bidirectional wavelength multiplexing optical transmission; and After the control of the state change, when receiving information that the optical reception failure is not cleared from the optical receiver provided in the one bidirectional wavelength multiplexing optical transmission device, the one bidirectional wavelength multiplexing optical transmission device includes It is determined that the optical reception failure of the optical receiver itself is the cause of the optical reception failure that occurred during the bidirectional wavelength multiplexing optical transmission, and when the information that the optical reception failure has been cleared is received, the other Check the optical reception failure of the optical receiver provided in the direction wavelength multiplexing optical transmission device, if the optical reception failure newly occurred in the optical receiver provided in the other two-way wavelength multiplexing optical transmission device, the The output failure of the optical transmitter included in the other bidirectional wavelength division multiplexing optical transmission device is determined to be the cause of the optical reception failure that occurred during the bidirectional wavelength division multiplexing optical transmission, and the other bidirectional wavelength division multiplexing optical transmission device If no optical reception failure has newly occurred in the optical receiver provided, the optical transmission path to which the optical receiver in which the reception failure has occurred was connected during the bidirectional wavelength division multiplexing optical transmission is the bidirectional wavelength. The method includes a step of determining that the cause is an optical reception failure that has occurred during multiplexed optical transmission. Also, the optical reception failure diagnosis method according to claim 10 of the present invention is a method for diagnosing an optical receiver having a different transmission wavelength from an optical receiver and branching output light from the optical transmitter into main output light and branch output light. A first optical branching means for outputting, and a first optical turnaround means for switching between the output light of the optical transmission line on the receiving side and the branched output light of the first optical branching means and connecting to the optical input of the optical receiver. A plurality of optical transceivers comprising: a multiplexer for multiplexing main output light of the first optical branching unit having different transmission wavelengths and outputting the multiplexed output light to an optical transmission line on a transmission side; A wavelength divisionally connected input light to the plurality of optical receivers, and a demultiplexer having substantially the same transmission wavelength characteristic as the multiplexer, and a light from the multiplexer to the transmission side optical transmission line. Second optical splitting means for splitting and outputting the output into main output light and split output light; By switching between branch output light of the second optical branching means comprises a second optical returning means for connecting to an optical input of said demultiplexer,
A transmission wavelength characteristic of the plurality of multiplexers connected to the transmission and reception side optical transmission lines and the transmission wavelength characteristics of the multiplexers are substantially the same, and a plurality of bidirectional wavelength division multiplexing optical transmission devices. An optical transmission system comprising: a failure monitoring control unit that monitors reception failures of the plurality of optical receivers and controls the switching connection of the first and second optical return units. Receiving information on occurrence of an optical reception failure from the optical receiver provided in one of the bidirectional wavelength division multiplexing optical transmission apparatuses performing bidirectional wavelength division multiplexing optical transmission; and Performing a first control for changing a connection state of the first optical turn-around means from a state at the time of the bidirectional wavelength-division multiplexing optical transmission; When receiving, from the optical receiver included in the one bidirectional wavelength multiplexing optical transmission device, information that the optical reception failure has not been cleared, the optical receiver itself included in the one bidirectional wavelength multiplexing optical transmission device It is determined that the optical reception failure is the cause of the optical reception failure that occurred during the bidirectional wavelength division multiplexing optical transmission, and when the information that the optical reception failure is cleared is received, the other bidirectional wavelength division multiplexing optical transmission device The optical bidirectional wavelength multiplexed light of the other bidirectional wavelength multiplexed optical transmission device is confirmed if the optical bidirectional wavelength multiplexed optical transmission device includes the optical bidirectional wavelength multiplexed light. Determining that the output failure of the optical transmitter included in the transmission device is the cause of the optical reception failure that has occurred during the bidirectional wavelength division multiplexing optical transmission, and the failure monitoring control means,
The connection state of the first optical return means provided in both bidirectional optical transmission devices is returned to the state at the time of the bidirectional wavelength multiplexing optical transmission, and the connection state of the second optical return means is changed to the bidirectional wavelength multiplexing light. Performing a second control for changing the state from the state at the time of transmission; and the failure monitoring control means, after the second control, transmitting the light from the optical receiver included in the one bidirectional wavelength division multiplexing optical transmission device. When receiving information for which the reception failure has not been cleared, it is determined that the optical demultiplexer of the one bidirectional wavelength division multiplexing optical transmission device is the cause of the optical reception failure that occurred during the bidirectional wavelength division multiplexing optical transmission. When receiving the information in which the optical reception failure is cleared from the optical receiver provided in the one bidirectional wavelength multiplexing optical transmission device, the optical reception of the optical receiver provided in the other bidirectional wavelength multiplexing optical transmission device is performed. Confirm failure In the case where an optical reception failure newly occurs in the optical receiver provided in the other bidirectional wavelength division multiplexing optical transmission device, the optical multiplexer provided in the other bidirectional wavelength division multiplexing optical transmission device has the bidirectional wavelength When it is determined that the cause of the optical reception failure occurred during multiplexed optical transmission, and when it is confirmed that no optical reception failure has newly occurred in the optical receiver provided in the other two-way wavelength multiplexing optical transmission device, An optical transmission line forming a transmission path between an optical transmitter included in the other bidirectional wavelength division multiplexing optical transmission device and an optical receiver included in the one bidirectional wavelength division multiplexing optical transmission device is the bidirectional wavelength division multiplexing. The method includes a step of determining that the cause is an optical reception failure that has occurred during optical transmission.

[0007]

Embodiments of the present invention will be described with reference to the drawings. The present invention provides an optical switch in an input portion of an optical signal and an optical branch in an optical output portion in a bidirectional optical transmission device, and provides a return function of input and output light by these, so that when an optical interruption failure occurs, It is characterized in that the cause of the failure is a transmission line or an optical transmission device, and that another determination of a transmitter / receiver can be easily performed by a remote operation. FIG. 1 shows a configuration of a bidirectional optical transmission system according to a first embodiment of the present invention. The transmission system performs bidirectional optical transmission using two fibers of the optical transmission line 50-1 and the optical transmission line 50-2.
It comprises one station (A station 1 and B station 2) and a center 3 for monitoring each station. The optical transmission devices included in the two stations may be terminal transmission devices or relay transmission devices. Optical transmission line 50
In some cases, one optical fiber is shared between upstream and downstream, and in other cases, separate upstream and downstream optical fibers may be used, but here, for simplicity, separate upstream and downstream transmission paths are assumed. The case is depicted. The same applies to the drawings describing the second and third embodiments below. Center 3
Receives the fault information 5 from each station and monitors the fault,
Device setting changes, in particular here the optical switch control signal 6
Is in a position where each station can be remotely operated by the monitoring system network 4. The A station and the B station each have an optical transmitter 10
An optical branch 40 for returning the output light of the optical transmitter to the optical transmission line 50 and the receiving device side of the local station and outputting the reflected light; an optical receiver 20; An optical switch 30 for switching between the signal returned by the station and transmitting the signal to the optical receiver.

The operation when a reception light level failure occurs in one of the two stations will be described. Now, it is assumed that an optical level reception failure (light interruption failure) has occurred in the optical receiver B20-2. The detection signal of the optical level reception failure is reported as failure information 5 from the B station 2 to the center 3 via the monitoring network 4. Upon receiving this, the center 3 sends the optical switch A to the stations A 1 and B 2 in the state shown by the dashed line in FIG.
20-1 and the optical switch B 20-2 are switched, and the optical switch control signal 6 is transmitted so that the transmission light of each station is turned back to its own station. On the B station 2 side, the return of the transmission light causes the optical receiver B20 which has generated an optical level reception failure.
-2, an optical transmitter B10 for which normal communication is guaranteed
-2 is input. The normality of the optical transmitter B10-2 is determined from the fact that the center 3 has not received the report of the optical level reception failure from the optical receiver A20-1 of the A station 1. The optical branch B40-2 and the optical switch B
If the failure of the received light level of the optical receiver B20-2 is released by the reception of the return signal light through the bypass route by 30-2, the center 3 determines that the optical receiver B20-2 has no cause of the failure. Therefore, the cause of failure is A station 1
The optical transmitter A10-1 on the side or the optical transmission path 50-1 becomes an obstacle. Conversely, if the received light level fault is not cleared,
The cause of the failure is determined to be a failure of the optical receiver B20-2 itself. On the other hand, the signal light of the optical transmitter A10-1 is repeatedly input to the optical receiver A20-1 in which normal communication is guaranteed at the station A side. With this input, the optical receiver A20-1
If the received light level failure does not newly occur, the center 3 determines that the optical transmitter A10-1 has no cause of failure, and determines that the true cause of failure is the optical transmission line 50-1. . Conversely, if a received light level failure of the optical receiver A20-1 newly occurs, the cause of the failure is determined to be the failure of the optical transmitter A10-1. As described above, the center 3 can isolate a failure point only by a remote operation through a network. In the above description, the case of the optical level reception failure from the optical receiver B has been described.
When an optical level reception failure occurs in the optical receiver A20-1 on the side, the cause of the failure can be similarly tracked. Further, the occurrence of a failure from both the optical receivers A and B may be reported to the center, but the probability of occurrence at the same time is extremely low, and the cause of the failure in the center is identified at high speed. Therefore, the cause can always be identified by the configuration of the present invention and the algorithm for determining the cause of the failure.

As another example of the first embodiment, the basic configuration is as described above. For example, the optical branches A and B are used with a branch ratio of 10: 1 or 20: 1. By doing so, it is possible to prevent a reduction in the level of transmission light transmitted to the transmission path, and to enhance the practicability. In addition, an optical switch may be used here instead of an optical branching unit. In addition, by setting the branching ratio more appropriately, inserting a fixed attenuator, etc., and setting the optical level to be returned to the local station to about the light receiving level at the time of normal communication between transmission devices, complete destruction of the optical transmission line and It is possible to determine not only a disconnection but also a failure due to a decrease in light level caused by subtle deterioration.

In the above embodiment, the number of stations monitored by the center 3 is two. However, a large number of stations, a large number of optical transmission devices, and a large number of optical reception devices are connected via a monitoring network. It goes without saying that the vessel can be monitored.

Further, the present invention is not limited to the above-described embodiment, but includes an optical transmitter and an optical receiver and performs other bidirectional transmission communication, such as a bidirectional wavelength division multiplexing optical transmission device or a frame-level optical transmission device. Multiplex separation of data (ADM: Add Drop)
The present invention can be widely applied to an optical network including a transmission device that performs multiplexing.
FIG. 2 shows a configuration of a bidirectional wavelength division multiplexing transmission system according to a second embodiment of the present invention. The transmission system includes two stations (A station 1 and B station 2) that perform bidirectional wavelength multiplexed optical transmission using two fibers of the optical transmission path 50-1 and the optical transmission path 50-2, and a center 3 that monitors each station. Consists of The center 3 can monitor the reception of the fault information 5 from each station and change the setting of the equipment of each station, particularly, in this case, the transmission of the optical switch control signal 6 by the monitoring network 4, and can remotely control each station. In a unique position. The A station, the B station, and the two stations each include an optical transmitter 10 that transmits signal light having different wavelengths and an optical receiver 20 that receives an optical signal having the same wavelength as the wavelength transmitted by the optical transmitter. Optical transmission devices 100-1 to 100-n, a multiplexer 200 for multiplexing the optical outputs from the respective optical transmission devices, and a receiver for transmitting the output light of the multiplexer to the optical transmission line and simultaneously transmitting the output light from the own station. The optical branch 400 which is output by folding back to the side, and the received signal multiplexed from the opposite station through the optical transmission line and the optical branch 40
An optical switch 300 for switching and outputting an optical signal returned by its own station according to 0, and a demultiplexer 500 for wavelength demultiplexing the output of the optical switch and outputting it to an optical receiver provided in an optical transmission device of each wavelength. Is done. The center 3 receives the fault information from all the optical receivers of the optical transmission devices of each wavelength of each station. The configuration of the first embodiment of FIG. 1 and the configuration of the second embodiment of FIG. 2 are different from each other only in that the number of optical receivers monitored in the center 3 is increased by the number of wavelengths. The operation of searching for a fault occurrence location when a reception light level fault has occurred is performed by the same algorithm as in the first embodiment, and it is possible to determine the location of the fault within or outside the station.

FIG. 3 shows a configuration of a bidirectional wavelength multiplex transmission system according to a third embodiment of the present invention. The configuration of FIG.
(The optical branch 400 and the optical switch 30)
0), the output light of each optical transmitter is split,
Each optical transmission device 100 is further provided with an optical branch 40 and an optical switch 30 for returning the signal within the device and receiving the switched light and the optical signal from the optical transmission line in an optical receiver. This makes it possible to separate the optical receiver / optical transmitter and the optical demultiplexer / optical multiplexer in the station in addition to the isolation of the cause of the failure in the transmission path / in the station and the optical transmission device. .

An operation when a reception light level failure occurs in one of the two stations will be described. Now, it is assumed that an optical level reception failure has occurred in the optical receiver B20-2-1. The detection signal of the optical level reception failure is reported as failure information 5 from the B station 2 to the center 3 via the monitoring network 4. The center 3 receiving this transmits an optical switch switching signal to both the A station 1 and the B station 2. FIG.
Attention is paid to the bidirectional optical transmission device 100-1-1 and the bidirectional optical transmission device 100-2-1 facing the bidirectional optical transmission device 100-1-1, and shows the switching state of the optical switches provided in these devices.

The center 3 first instructs the switching state shown in FIG. That is, when the failure cause location is the optical transmission device 1
The optical switch A30-1-1 and the optical switch B3 in the optical transmission device are used to distinguish between the inside of the optical transmission device and the transmitting side after the demultiplexer.
0-2-1 is set to a state shown by a dashed line, so that it is turned back in its own device. Then, the optical switch a300-
1. The optical switch b300-2 sends out the optical switch control signal 6 so as to maintain the transmission path side. On the side of the B station 2, the optical receiver B20-2-1 which has generated an optical level reception failure by returning the transmission light in its own device is provided with:
The signal light from the optical transmitter B10-2-1 in which normal communication is guaranteed is input. In this connection state, the optical receiver B2
If the received light level failure of 0-2-1 is cleared, the center 3 determines that the optical receiver B20-2-1 has no cause of failure. Therefore, the cause of the failure is the optical transmission device 1 on the A station 1 side.
The transmission side of 00-1-1 or the optical transmission path 50-1 or the branching unit a500-2 of the own station B station 2 becomes an obstacle. Conversely, if the received light level fault is not cleared, the cause of the fault is determined to be the fault of the optical receiver B 20-2-1 itself. On the other hand, A
The optical receiver A20- in which normal communication is guaranteed at the station side
1-1, the signal light of the optical transmitter A10-1-1 is looped and input. By this input, the optical receiver A20-1-1
If the received light level failure does not newly occur, the center 3 determines that the optical transmitter A10-1-1 has no cause of failure, and the true cause of the failure is the multiplexer a200-1 of the station A or The optical transmission line 50-1 or the branching station b500-2 of the station B is determined. Conversely, if a received light level failure of the optical receiver A20-1-1 has newly occurred, the cause of the failure is determined to be a failure of the optical transmitter A10-1-1.

Next, there is no obstacle in the optical receiver B 20-2-1 and the optical transmitter A 10-1-1, and the optical receiver B 20-2-1 and the optical transmission line 50-1 or the demultiplexer b 500-2 have no obstacle. When it is determined that there is, the center 3 instructs the switching state of the optical switch in FIG. That is, the optical switch A30-1-1 and the optical switch B30-2-1 in the optical transmission device.
Is returned to the state shown by the dashed line in FIG. 4 (B) to cancel the return in the own device, and the optical signal from the demultiplexer 500 is input to each optical receiver 20. Then, the optical switch a 300-1 and the optical switch b 300-2 are switched, and the optical switch control signal 6 is transmitted so as to return to the local state. On the B station 2 side, due to the return of the transmission light within the own station, the optical receiver B20-2-1 that has issued the optical level reception failure receives the signal from the optical transmitter B10-2-1 whose normal communication is guaranteed. The multiplexer b20 in which the signal light is normal
0-2, input via the duplexer b500-2 suspected of having a fault. The optical branch b400-2 and the optical switch b
If the reception light level failure of the optical receiver B20-2-1 is cleared by the reception of the return signal light through the detour path by the 300-2, the center 3 demultiplexer b500-2.
Is determined to have no failure cause. Therefore, the cause of the failure is a failure on the transmitting side of the A station 1, that is, the multiplexer a200-1 or the optical transmission line 50-1. Conversely, if the received light level fault is not cleared, the cause of the fault is the demultiplexer b500
-2 is determined to be a failure. Then, the A station transmits the optical transmitter A to the optical receiver A 20-1-1 in which normal communication is guaranteed.
The multiplexer a20 in which the signal light of 10-1-1 is suspected to be a failure.
0-1, optical branch a400-1, optical switch a300-
1. Optical switch A30-1-1 and normal duplexer a5
Returned input via 00-1. As a result of this input, if a reception light level failure has not occurred in the optical receiver A20-1-1, the center 3 determines that the multiplexer a200-1 has no failure cause, and the true failure cause is the optical transmission. Road 50
It is determined to be -1. Conversely, the optical receiver A20-1-1
If a reception light level failure newly occurs in the above, the failure cause is determined to be a failure of the multiplexer a300-1.

Even if the optical transmitter A20-1-1 of the A station 1 issues the failure information of the received light level failure, the center 3 can search and find the cause of the failure by the same procedure.
As described above, the center 3 can isolate a faulty part only by a remote operation to all the bidirectional optical transmission devices of the stations A and B via the monitoring network 4 and further to a large number of stations. it can.

[0017]

As described above, according to the present invention, an optical switch is provided at an input portion of an optical signal and an optical branch is provided at an optical output portion in a bidirectional optical transmission apparatus, and input / output light is returned by these components. By providing the function, it is possible to easily determine whether the cause of the failure is the transmission line or the optical transmission device at the time of occurrence of the optical disconnection failure, and further perform another determination of the transmitter / receiver by remote operation. This determination can be made more accurately and easily, which has the effect of greatly reducing the maintenance cost of the optical transmission system.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an optical transmission system according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of an optical transmission system according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of an optical transmission system according to a third embodiment of the present invention.

FIG. 4 is a diagram illustrating an optical switch switching state in an optical transmission system according to a third embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration of a general bidirectional optical transmission system.

FIG. 6 is a diagram illustrating a conventional method for detecting a failure by loopback in a bidirectional optical transmission system.

[Description of Signs] 1 A station 2 B station 3 Center 4 Monitoring network 5 Fault information 6 Optical switch control signal 10 Optical transmitter 20 Optical receiver 30 Optical switch 40 Optical branch 50 Optical transmission path 51 Optical transmission path 52 Optical transmitter A 53 Optical receiver A 54 Optical receiver B 55 Optical transmitter B 57 Optical switch 58 Optical switch controller 59 Failure determiner 60 A station 70 B station 100 Bidirectional optical transmission device 200 Multiplexer 300 Optical switch 400 optical branching 500 branching filter

Continued on the front page F term (reference) 5K002 AA05 BA06 DA04 EA07 EA32 GA04 5K035 AA04 AA07 DD01 GG06 GG14 JJ01 5K042 CA10 DA16 DA33 EA01 EA07 EA15 FA01 FA21 LA13 LA15 NA03

Claims (10)

[Claims] 1. An optical transmitter, an optical receiver, and a unit for returning a part of an optical output from the optical transmitter to the optical receiver,
A plurality of bidirectional optical transmission devices connected to the transmission side and the reception side optical transmission line, and monitors a reception failure of the plurality of optical receivers included in the plurality of bidirectional optical transmission devices, and monitors the optical return means. An optical transmission system comprising a fault monitoring control unit for performing control. 2. The optical branching unit, wherein the optical turning-back unit outputs an optical output output from the optical transmitter to the optical transmission line on the transmitting side into a main output light and a split light obtained by splitting a part of the optical output. 2. The apparatus according to claim 1, further comprising means for switching the output light of the optical transmission path on the receiving side and the output light of the branching means to connect to the optical input of the optical receiver. Optical transmission system. 3. The optical transmission system according to claim 1, wherein the control performed by the fault monitoring control means is the control of the switching connection of the optical turn-back means. 4. The apparatus according to claim 1, wherein a branching ratio of the means for partially branching the optical output output from the optical transmitter to the optical transmission line on the transmission side by the optical turn-back means is smaller than -10 dB. 3. The optical transmission system according to 2. 5. An optical level at which the optical turn-back means connects the branch output light to an optical input of the optical receiver is substantially equal to an input optical level at the time of the bidirectional transmission of the optical receiver. 3. The optical transmission system according to claim 1, wherein 6. An optical transmitter, an optical receiver, and an optical output output from the optical transmitter to an optical transmission line on a transmission side, as main output light and split light obtained by splitting a part of the optical output. An optical branching means for switching the optical transmission path output light on the receiving side and the branching output light of the branching means to connect to the optical input of the optical receiver; A plurality of bidirectional optical transmission devices connected to a transmission path, and a plurality of the optical receivers included in the plurality of bidirectional optical transmission devices are monitored for reception failure to control the switching connection of the optical return unit. In an optical transmission system including a failure monitoring control unit, the failure monitoring control unit transmits information on occurrence of an optical reception failure from the optical receiver included in one of the bidirectional optical transmission devices performing bidirectional optical transmission with each other. Receiving the error message; A step in which the harm monitoring control means performs control for changing the connection state of the two optical return means from the state at the time of the bidirectional optical transmission, and the failure monitoring control means changes the connection state of the optical return means. After the control of, when receiving information that the optical reception failure is not cleared from the optical receiver provided in the one bidirectional optical transmission device, the light of the optical receiver itself provided in the one bidirectional optical transmission device It is determined that the reception failure is the cause of the optical reception failure that occurred during the bidirectional optical transmission, and when the information that the optical reception failure has been canceled is received, the optical receiver of the other bidirectional optical transmission device is Check the optical reception failure, and if an optical reception failure newly occurs in the optical receiver provided in the other bidirectional optical transmission device, the output failure of the optical transmitter provided in the other bidirectional optical transmission device Is said If it is determined that the cause is an optical reception failure that occurred during the optical transmission, and if no optical reception failure has newly occurred in the optical receiver provided in the other bidirectional optical transmission device, the bidirectional optical transmission Diagnosing an optical reception failure characterized in that the optical transmission path to which the optical receiver in which the reception failure has occurred is connected is a cause of an optical reception failure occurring during the bidirectional optical transmission. Method. 7. A plurality of optical transceivers each having an optical receiver and an optical transmitter having a different transmission wavelength, and multiplexing the outputs of the plurality of optical transmitters having different transmission wavelengths into an optical transmission path on a transmission side. An output multiplexer, and a wavelength divider that wavelength-multiplexed input light is wavelength-separated to the plurality of optical receivers and connected to each other, and the multiplexer has substantially the same transmission wavelength characteristic as the multiplexer. An optical branching unit for branching and outputting an optical output output to a transmission side optical transmission line into a main output light and a branch output light, and switching between a reception side optical transmission line output light and the branch output light of the branching unit. Bidirectional wavelength-division multiplexed light having optical return means connected to the optical input of the demultiplexer, and having a plurality of the plurality of multiplexers connected to the transmission and reception side optical transmission lines, having substantially the same transmission wavelength characteristics. A transmission device, and the plurality of optical receivers included in the plurality of bidirectional wavelength division multiplexing optical transmission devices An optical transmission system comprising: a failure monitoring control unit that monitors a reception failure of the optical switching unit and controls the switching connection of the optical loopback unit. 8. An optical transmitter having a transmission wavelength different from that of an optical receiver, first optical branching means for branching and outputting output light from the optical transmitter into main output light and branch output light, and light on the receiving side. A plurality of optical transceivers including first optical turn-around means for switching between transmission line output light and branch output light of the first optical branch means and connecting to the optical input of the optical receiver; A multiplexer for multiplexing main output lights of the first optical branching means having different wavelengths and outputting the multiplexed light to an optical transmission line on a transmission side; and a wavelength separator for wavelength-multiplexed input light to the plurality of optical receivers. A demultiplexer having substantially the same transmission wavelength characteristic as the multiplexer, and branching and outputting the optical output from the multiplexer to the transmission-side optical transmission line into main output light and branch output light. A second optical branching unit, switching between the output light of the optical transmission path on the receiving side and the branched output light of the second optical branching unit, A second optical return means connected to the optical input of the demultiplexer; and a plurality of the multiplexers connected to the transmission and reception side optical transmission lines, the transmission wavelength characteristics of which are substantially equal to each other, and the bidirectional wavelengths are substantially the same. A fault that monitors a reception fault of the multiplexed optical transmission device and the plurality of optical receivers included in the plurality of bidirectional wavelength multiplexing optical transmission devices and controls the switching connection of the first and second optical return units. An optical transmission system comprising a monitoring control means. 9. A plurality of optical transceivers each having an optical receiver and an optical transmitter having a different transmission wavelength, and multiplexing outputs of the plurality of optical transmitters having different transmission wavelengths to form an optical transmission path on a transmission side. An output multiplexer, and a wavelength divider that wavelength-multiplexed input light is wavelength-separated to the plurality of optical receivers and connected to each other, and the multiplexer has substantially the same transmission wavelength characteristic as the multiplexer. An optical branching unit for branching and outputting an optical output output to a transmission side optical transmission line into a main output light and a branch output light, and switching between a reception side optical transmission line output light and the branch output light of the branching unit. Bidirectional wavelength-division multiplexed light having optical return means connected to the optical input of the demultiplexer, and having a plurality of the plurality of multiplexers connected to the transmission and reception side optical transmission lines, having substantially the same transmission wavelength characteristics. A transmission device, and the plurality of optical receivers included in the plurality of bidirectional wavelength division multiplexing optical transmission devices In the optical transmission system comprising a failure monitoring control means for monitoring a reception failure and controlling the switching connection of the optical return means, the failure monitoring control means performs bidirectional wavelength multiplexing optical transmission with each other. Receiving information on the occurrence of an optical reception failure from the optical receiver included in the bidirectional wavelength division multiplexing optical transmission device; and the failure monitoring control means sets the connection state of both optical return means to the bidirectional wavelength division multiplexing. Performing a control for changing from a state at the time of optical transmission, and the fault monitoring control means, after controlling the change of the connection state of the optical return means, the optical reception provided by the one bidirectional wavelength multiplexing optical transmission device. When the information that the optical reception failure has not been cleared is received from the receiver, the optical reception failure of the optical receiver itself included in the one bidirectional wavelength division multiplexing optical transmission apparatus is caused by the optical reception failure. When it is determined that the cause is an optical reception failure that has occurred during wavelength-division multiplexed optical transmission, and when the information on which the optical reception failure has been cleared is received, the light of the optical receiver included in the other bidirectional wavelength-division multiplex optical transmission device is transmitted. Confirming a reception failure, and when an optical reception failure newly occurs in the optical receiver provided in the other bidirectional wavelength division multiplexing optical transmission device, an optical transmitter included in the other bidirectional wavelength division multiplexing optical transmission device Is determined to be the cause of the optical reception failure that occurred during the bidirectional wavelength division multiplexing optical transmission, and a new optical reception failure has occurred in the optical receiver of the other bidirectional wavelength division multiplexing optical transmission device. If not, the optical transmission path to which the optical receiver in which the reception failure has occurred during the bidirectional wavelength division multiplexing optical transmission is the cause of the optical reception failure occurring during the bidirectional wavelength division multiplexing optical transmission. Including the step of determining Optical receiving fault diagnosis method characterized by. 10. An optical transmitter having a transmission wavelength different from that of an optical receiver, first optical splitting means for splitting and outputting output light from the optical transmitter into main output light and split output light, and light on the receiving side. A plurality of optical transceivers including first optical turn-around means for switching between transmission line output light and branch output light of the first optical branch means and connecting to the optical input of the optical receiver; A multiplexer for multiplexing main output lights of the first optical branching means having different wavelengths and outputting the multiplexed light to an optical transmission line on a transmission side; and a wavelength separator for wavelength-multiplexed input light to the plurality of optical receivers. A demultiplexer having substantially the same transmission wavelength characteristic as the multiplexer, and branching and outputting the optical output from the multiplexer to the transmission-side optical transmission line into main output light and branch output light. Switching between the second optical branching unit, the output light of the optical transmission path on the receiving side, and the branched output light of the second optical branching unit, A second optical return means connected to the optical input of the multiplexer / demultiplexer, wherein a plurality of the multiplexers connected to the transmission and reception side optical transmission lines have substantially the same bidirectional transmission wavelength characteristics. The wavelength multiplexing optical transmission device and the plurality of bidirectional wavelength multiplexing optical transmission devices monitor reception failures of the plurality of optical receivers and control the switching connection of the first and second optical return units. In the optical transmission system including the fault monitoring control means, the fault monitoring control means performs bidirectional wavelength multiplexing optical transmission with each other. Receiving the information of the occurrence of the error, and performing the first control for changing the connection state of both the first optical turn-around means from the state at the time of the bidirectional wavelength multiplexing optical transmission. line A step, wherein the fault monitoring control means, after the first control, when the light receiving failure from the optical receiver provided in the said one-way wavelength division multiplexing optical transmission apparatus has received the information that has not been canceled,
It is determined that the optical reception failure of the optical receiver itself included in the one bidirectional wavelength division multiplexing optical transmission device is the cause of the optical reception failure that occurred during the bidirectional wavelength division multiplexing optical transmission, and the optical reception failure is released. When the received information is received, the optical reception failure of the optical receiver provided in the other bidirectional wavelength division multiplexing optical transmission device is confirmed, and the optical reception failure is detected in the optical reception unit provided in the other bidirectional wavelength division multiplexing optical transmission device. Is newly generated, a step of determining that the output failure of the optical transmitter provided in the other bidirectional wavelength division multiplexing optical transmission device is the cause of the optical reception failure occurred during the bidirectional wavelength division multiplexing optical transmission, The failure monitoring control means returns the connection state of the first optical return means provided in both bidirectional optical transmission devices to the state at the time of the bidirectional wavelength division multiplexing optical transmission, and connects the second optical return means. State Performing a second control for changing from a state at the time of wavelength-division multiplexing optical transmission, and the failure monitoring control means, after the second control, the optical control of the one bidirectional wavelength-division multiplexing optical transmission device When receiving information from the receiver that the optical reception failure has not been cleared, the optical demultiplexer of the one bidirectional wavelength division multiplexing optical transmission device causes an optical reception failure that occurred during the bidirectional wavelength division multiplexing optical transmission. Is determined, and when the information on which the optical reception failure has been cleared is received from the optical receiver provided in the one bidirectional wavelength multiplexing optical transmission device, the optical reception provided in the other bidirectional wavelength multiplexing optical transmission device is performed. The optical bidirectional wavelength division multiplexing optical transmission device is provided with the optical bidirectional wavelength division multiplexing optical transmission device. Optical multiplexer It is determined that the cause is an optical reception failure that has occurred during bidirectional wavelength division multiplexing optical transmission, and it is confirmed that no optical reception failure has newly occurred in the optical receiver provided in the other bidirectional wavelength division multiplexing optical transmission device. In this case, the optical transmission line that constitutes a transmission path between the optical transmitter provided in the other bidirectional wavelength multiplexing optical transmission device and the optical receiver included in the one bidirectional wavelength multiplexing optical transmission device is the optical transmission line. A method for diagnosing an optical reception failure, comprising the step of determining that the cause is an optical reception failure that has occurred during bidirectional WDM optical transmission.